http proxy problem of QWebEngineView

Hi, I'm trying to port my Qt application from Webkit to WebEngine, but I'm failing to find a way to set proxy for QWebEngineView.
I hava tried to set my Application's proxy as follows. But it's also failed to access the web page.
QNetworkProxy m_networkProxy;
QNetworkAccessManager *m_networkAccessManager;
m_networkAccessManager = new QNetworkAccessManager;